1. Field of the Invention
The present invention relates to a wideband amplifier, and more particularly, to a radio transceiver, a semiconductor integrated circuit adapted for implementer the radio transceiver, and a wideband amplification method.
2. Description of the Related Art
A differential amplifier is used by radio transceivers such as a wireless LAN device or other information transceiver. The differential amplifier consists of a buffer and an amplifier connected to the output side of the buffer. As an amplifier, the differential amplifier is used generally. The differential amplifier uses dual transistors both having parasitic input capacitance, which is an adjunct of a base terminal. A cross-coupled compensator is employed in order to compensate for input capacitance. The cross-coupled compensator consists of two amplification transistors. Two amplification transistors have a collector terminal and a base terminal connected each other. In addition, two amplification transistors have compensation capacitor between each other's base and emitter terminals. The compensation current flows junction capacitance or mirror capacitance of input transistors. In a cross-coupled compensator, amplification transistors have voltage drop between the base and emitter terminals, because the amplification transistors are connected between the output side of the buffers and grounds. The cross-coupled compensator is not suitable for low voltage operation. In addition, dynamic range of the differential amplifiers becomes narrow, because the differential dual transistors have own base and collector terminals which are connected each other. The differential amplifier is not suitable for large signal applications. For example, the voltage of the base and emitter terminals of the transistor is supposed to be 0.7V, the saturation voltage of a transistor is supposed to be 0.2V, and the dynamic range of the differential amplifiers is to be 1.0Vpp. The voltage of the base and emitter terminals decreases 0.1V in a high temperature. In other words, the dynamic range of the amplifier becomes narrower when the junction temperature becomes high. This time, dynamic range in differential operation becomes 0.8Vpp.